| Oldfield Gap | N Graham County between Yellow Creek Mountains and Fork Ridge. |
| Oldfield Gap | on the Madison-Yancey county line near Indian Creek. |
| Oldfield Swamp | rises in S Robeson County and flows SE into Hog Swamp. |
| Oldfields Township | SW Ashe County. Named for muster ground and drill field used by Benjamin Cleveland during the Revolution. |
| Oldham | community in N Forsyth County served by post office, 1883-1901. |
| Olds | community in S Currituck County. Known locally as Olds Hill for a sand hill nearby. |
| Olds Township | E central Greene County. Named for the Olds family whose members moved there after 1779. |
| Oldwoman Branch | rises in W Pitt County and flows SE into Little Contentnea Creek. |
| Olga | community in W Pender County served by post office, 1900-1908. |
| Olin | town in N central Iredell County. Est. and inc. 1855 as New Institute when Brantley York and Baxter Clegg opened an academy there. Reincorporated 1857 as Olin in honor of Stephen Olin, Methodist educator. Inc. again in 1905, but long inactive in municipal affairs. |